Symbol display system for messages received in signal form

ABSTRACT

Alpha-numerical signals are indicated on the face of a cathode ray tube, the scanning of which is controlled by stored signals derived from photo-sensitive sensors, arranged in a matrix, and exposed to light from an electro-luminescent source, addressing a specific field in a mask, the mask carrying on its fields representations of the alpha-numerical symbols.

United States Patent Fouche et a1.

[15] 3,656,147 [451 Apr. 11, 1972 [54] SYMBOL DISPLAY SYSTEM FOR MESSAGES RECEIVED IN SIGNAL FORM [72] Inventors: Yvon Fouche, Chatou; Jean Dansac, Paris,

both of France [73] Assignee: Compagnie Internationale Pour LInformatique [22] Filed: Jan. 21, 1969 [21] Appl. No.: 792,664

[30] Foreign Application Priority Data July 28, 1968 France ..137376 [52] U.S. Cl ..340/324 A, 250/219 0, 315/169 TV [51] Int. Cl ..G06f 3/14 [58] Field ofSearch ..340/324.1, 324A, 324R; 178/68, 6; 315/169 TV; 250/217 CR, 219 Q, 219

[56] References Cited UNITED STATES PATENTS 2,509,045 5/1950 Salisbury ..178/6.8 X 3,324,346 6/1967 Stone ....340/324 X 1 3,349,172 10/1967 Mauchel 340/324 X 3,435,138 3/1969 Borkan "178/71 3,345,458 10/1967 Cole et al. ...340/324 A X 3,388,391 6/1968 Clark ..340/324 A Primary Examiner--David L. Trafton Attorney-Stephen H. Frishauf [57] ABSTRACT Alpha-numerical signals are indicated on the face of a cathode ray tube, the scanning of which is controlled by stored signals derived from photo-sensitive sensors, arranged in a matrix, and exposed to light from an electro-lurninescent source, addressing a specific field in a mask, the mask carrying on its fields representations of the alpha-numerical symbols.

16 Claims, 9 Drawing Figures PATENTEDAPR 11 m2 SHEET 3 [IF 6 m M ru wxv SF 5 r: L a W .I all: fiK a? mm w mwmmww m l m if. a Q

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SHEETRUFG T D6 WHHHJUUUULMHI t T A Fun 1 nu llll t E llll mn v I t SYMBOL DISPLAY SYSTEM FOR MESSAGES RECEIVED IN SIGNAL FORM The present invention relates to symbol display systems, and more particularly to systems to display alpha-numerical characters by scanning an electron beam over the face of a cathode ray tube.

The development of digital computers requires, as a corrollary, read-out devices which are rapid and can keep pace with the output of the computer. It has been proposed to present computer output on the face of cathode ray tubes, that is without the intervention of the inertia-introducing electromechanical parts, so that alpha-numerical characters, curves, and other symbols will be displayed.

Basically, three ways of deriving symbols to be displayed have been proposed. In one, a mask, which may be tubular, is provided which permits only a part of the beam which is emitted to pass,the portion of the beam passing the mask corresponding to the desired symbol. The position of the symbol on the screen is controlled, so that it may fit against predetermined zones on the screen itself. In accordance with another system, the symbol is defined by luminous points, of large number, subdivided into a field or into a grid network formed of lines and columns. The third system uses a continuous trace, in the form of Lissajous figures, in order to produce the symbols, by providing appropriate deflection to the original pattern.

The system of the present invention utilizes the concept of the second one of the above-identified groups, the symbol being formed by modulating the intensity of different elementary areas within a field on which the symbol is to be presented. In contrast, however, masking tubes are not used; the portion of the system producing the display signals is separated from the display tube itself. Several cathode ray tubes (CRT) may be connected to one single signal generator. Scanning of one or more of the CRTs is uniform and may be along a spiral, or linear trace as in ordinary television reproduction. The signals may be obtained by electronic scanning, which is very fast and provides a high degree of resolution, of a model on which the desired symbol is reproduced. The signals may be obtained by electronically reading a matrix, such as a magnetic core matrix, associated with digital circuits. The matrix may correspond to a predetermined trace line and form a symbol memory, which controls the display of a predetermined number of different symbols. A message to be displayed comprises a predetermined number of such symbols, separately, and displayed on the screen of a cathode ray tube at predetermined locations. Control apparatus is provided, operating in synchronism with the scanning of the cathode ray tube. The main element thereof is a memory, which may be termed an operating, or message memory, in which the information of an entire message may be stored, to be read-out as desired and displaying the appropriate signals at predetermined locations on the X and Y axes on the CRT.

The known solutions to display symbols by scanning fields rapidly become complex particularly in connection with readout of memories, when the locations or read-out increases and when the numbers of symbols to be presented increases. One of the solutions consists to break down each of the symbols into segments, which are either light or dark, along scanning lines on the screen on which the character is displayed. The symbol of the display is generated by a signal having a duration which corresponds to the time of scanning along the length of the segment. The overall visibility of the parts of different segments then corresponds to luminous points on a field.

It is accordingly an object of the present invention to provide a symbol display system on which the control is simplified and particularly the electronic addressing circuitry for a given number of symbols is of reduced complexity.

It is an additional object of the present invention to provide a display system in which the shape of the symbols to be displayed may be easily changed, for example by change of the font of alpha-numerical characters, without change in the electronic circuitry.

SUBJECT MATTER OF THE PRESENT INVENTION Briefly, an optical electronic system is provided in which a mask carries a representation of the different symbols in the form of transparencies. One or more eIectro-luminescent sources illuminate the mask. One or more matrices of photoelectric detectors are located to be illuminated by light from the electro-luminescent sources through the mask; the photo detectors are arranged to correspond to a field to be scanned, for presentation of a character, in the form of a raster in lines and columns. Means are provided to focus the luminous radiation and to address only a single symbol on the matrix. The product of the number of sources and of matrices may then be equal to the total number of symbols carried by the mask.

In accordance with the feature of the present invention, a column of electro-luminescent sources equal to the number of lines of the mask is provided, each illuminating a single line of symbols on the mask. Matrices then are arranged in lines, equal to the number of columns on the mask. The optical energization is then arranged such that the symbols on a line of the mask are projected in accordance with the rank on the line of the'matrices, so that a single symbol can be selected.

Electro-luminescent sources are preferably solid state light emitting diodes, having optical directive lenses as part thereof, such as gallium-arsenide diodes. The matrices preferably con tain a raster of identical photo-detectors, arranged adjacent each other in a sufficient number to provide the desired definition upon display of the symbol.

In accordance with another embodiment of the present invention, the focusing means include an optical arrangement consisting of compound lenticular optics, similar to fly s eye optics, and having a plurality of identical enlarging objectives, the number of these objectives being equal to the total number of symbols carried on the mask.

The structure, organization, and operation of the invention will now be described more specifically with reference to the accompanying drawings, wherein:

FIG. 1 illustrates the arrangement of character fields, or blocks, on a message line;

FIG. 2 is a schematic block diagram of a display system in accordance with the present invention;

FIG. 3 illustrates the arrangement for reproduction of a symbol, namely the letter F";

FIG. 4 are wave forms used in the system;

FIG. 5 is a schematic presentation of the optical system;

FIG. 6 is a schematic diagram of logic circuits for use with the arrangement of FIG. 5;

FIG. 7 illustrates display of a pair of consecutive characters and wave forms useful in connection therewith;

FIG. 8 is a partial schematic view of the optical arrangements of FIG. 5 illustrating complementary focusing; and

FIG. 9 is a simplified schematic diagram illustrating an optical matrix in arrangement in combination with a flat memory mask.

The display system is intended to convert messages presented thereto in numerical form in order to obtain a television image read-out. The display system receives the information in codes, representing the symbols to be displayed, such as alpha-numerical characters, in the form of read-out signals from a computer, a teleprinter receiver or the like. This coded information further includes address data for each character, representing the position of the particularcharacter on the presentation screen. In order to define the position of a character on the screen, it is sub-divided into imaginary horizontal message lines and further, into successive character positions on these message lines, which form lines of a text. Each message line is associated with a number n, n being fixed and corresponding to the scanning lines for each field if the scanning raster is horizontal, as is customary inordinary televison tubes, or 2n scans in an interlace pattern.

The position of the line of the text 1', for example, which is schematically illustrated in FIG. 1, may thus be defined by an ordinate Yi with respect to the first line which is being scanned. Each line is divided into p subdivisions which, in order to simplify the construction, may be considered fixed; each number p defines the address of a subdivision, or elementary area, or character block within which a symbol may be inscribed. The location of such a subdivision, or a character block on a message line i may thus be defined by an abscissa Xj in the vertical from a point of origin of the first elementary area or subdivision of a line having an ordinate Yi. The coordinates Xj, Yi thus will determine the location of a character to be inscribed in a corresponding character block.

The number of 2n of lines which scan any particular line of text is fixed; the spacing between successive lines of text also will be fixed and the total lines of message which may be inscribed on a screen can thus be determined. Since one knows the number p of character blocks or subdivisions on each line, different characters to be inscribed on the screen can be assigned coordinates of the type Xj, Yi, represented by an address code in numerical form and defining the number of the message line as well as the number of the corresponding character block.

Referring now to FIG. 2: An input unit 1 provides information data in display code, to a control unit 2 in which the codes are analyzed and stored or recorded in a message memory 3 with addresses corresponding to the coordinates of the characters to be displayed on the screen. When the messages are stored in memory 3, in coded form, control unit 2 triggers read-out of the different addresses of the memory 3, in synchronism with the scanning of the display screen in order to obtain, at the point when the scanning starts, a representation of the coded information stored in the address memory and corresponding to the location of the specific characters within the character blocks. Let it be assumed that scanning is horizontal, that is, in accordance with the usual television pattern. Control unit 2 is thus controlled by the line synchronization signals applied thereto over line SL, and the field, or vertical synchronization signals applied over line ST of the television scanning raster. The display system produces, as a function of the information read from memory 3, video signals controlling display of the characters on the screen. Unit 4, connected to memory 3 over a character decoding element, which will be described in detail below, converts the decoded signals to video signals which produce, during scanning of each portion of a line of the screen within the respective character blocks, a series of pulses representing traces of light, as well as a series of blocking or suppression pulses in accordance with the shape of the signals to be inscribed in each particular character block or subdivision. Unit 4 further receives from control line 2, over a control unit 5, a line distribution control signal and, further, over a timing control line 6, a clock or timing control signal. The control signals provided to unit 4, respectively, indicate at all times the number of the line being scanned and, within the line itself, provide regularly recurring pulses corresponding to space within the elementary subdivisions, or character blocks along a line. These pulses define the instant, in time, of scanning of successive points, uniformly distributed over each line, of a character block. These points on a screen are thus illuminated or not, depending on the shape of the character to be described within a character block, or subdivision. For each possible shape of character or symbol, unit 4 thus provides a succession of control signals to command bright" or black" output of the CRT, coincident with the pulses provided thereto, in time distribution, and corresponding respectively to whether the elementary points on the tube are to be illuminated or not.

The illumination signals, and the extinction signals, corresponding to the characters to be inscribed at a particular location on the screen, are applied to an output circuit 8 which delivers over a line 9 video signals which eventually control the display. The circuit 8 provides video signal of amplitude which varies between a pair of constant values, that is bright" or black". The display of the character is thus not accomplished by a point system, but rather by segments of variable length arising within the character blocks, as specifically illustrated in connectionwith FIG. 3, showing the letter F The character block of FIG. 3 has the coordinates Xj, Yi. The letter F" is represented on each one of the 2 n lines of scanning L1 to L2n. Letter F" is limited at the right, and left, by two vertical lines abscissa x1 to xq. These abscissa positions x1 to xq correspond to pulses furnished by the clock source, and derived from control unit 2.

FIG. 4 illustrates pulses D6 furnished by the clock source, during each period T of scan of the portions of the lines L1 to L2n, between the abscissa lines Xj and Xj-H. The bright pulses A1 are shown in the next line for line L,, furnished by the matrix 4 in order to form the letter F The video output signal is finally illustrated on the third line of FIG. 4, line V1, as delivered by circuit 8 during the course of the scanning of the line L1.

It is seen immediately that pulses D6, if taken sufficiently close together, can provide excellent precision of the definition of the segments to be displayed and consequently of the representation of the characters, without extending the spectrum of the video signals since the frequency of the pulses within the signals usually have a duration several times higher than the pulse duration of the period D6.

The present invention is particularly concerned with the unit 4 (FIG. 2). The specific circuitry of control unit 2, and memory unit 3 is not described in detail, such elements being well-known in the art. This part of the system is only briefly described, by way of example, in order to facilitate the understanding of the entire apparatus. Coded information supplied by input unit 1 includes two elements. As discussed above, the part of the coded information K, identifies the character, or symbol to be displayed; the other part identifies the address, that is the coordinates X, Y of the location on the face of the CRT where the character is to be displayed. Each of the characters K may be defined by a binary number, of fixed word length, to which an address, likewise in binary form, and also of fixed word length is attached. For example, six binary digits may represent a maximum of 63 different characters. A circuit, such as a control programming circuit, records the information in memory 3, and controls the writing circuits of the memory in such a way that each character is recorded at an address of memory 3 corresponding to coordinates X, Y assigned to the particular symbol or character. Memory 3 may consist of any kind of bistable circuits, for example may be made of matrices of ferrite cores, such as a plurality of planes of ferrite cores in parallel. The number of such core planes may be equal to the number of digits representing a character. The digits representing character information are thus recorded in parallel planes at a position equivalent to the coordinates X, Y which the character is to assume on the display screen. The number of cores on each storage card, representing a plane, thus must be at least equal to the numbers of coordinate positions X, y which are possible. If input unit 1 provides outputs of characters so that they are successively recorded on the same message line, the coordinates X,Y may be set to be relative to the coordinate position of the first character, and from then on the number of the message line, and the information codes need only contain information regarding format, indicating, for example, blank or empty spaces along a line.

After all the information for each character has been supplied by input 1, and is recorded in memory 3, reading circuits permit extraction of the necessary information and the generation of the display signals. Other circuits, well known in the art, may be utilized to re-record automatically the information just read into the memory, so that no information is lost. After the information has been displayed, the entire memory may be erased, as well known in the art, and by circuitry not shown specially.

, Control unit 2 also includes synchronization circuits which supply signals indicating, during scanning of the read-out screen, on the one hand the period of the scanning of the different lines of the text to appear on the screen, and further the period of scanning of the different character blocks themselves, within any one of the scanned lines. These signals are formed by pulses Iy to synchronize the lines of the text and appear at the start of the scan of each of the lines; and further by block-character synchronization pulses Ix, which appear at the start of the scan of each of the portions of the lines at which a character block appears. The first pulses therefore appear at the instance of time when scanning of a line having the ordinate Yi on the screen begins, the ordinate defining the position of the different lines of the message to be displayed. Similarly, the pulses Ix appear at an instant of time when, within the spacing of the horizontal line of the message, the scanning beam has reached a specific abscissa position Xj, at which the block-character positions occur.

These, synchronization circuits generating the pulses ly and Ix are controlled by the screen synchronization signals, to indicate the beginning of each scanning cycle, as well as the beginning of scanning of successive lines. In the example here chosen, display is on a television-type screen and thus the synchronization signals are line synchronization (SL) and field synchronization (ST) signals. The pulses Ix are generated by means of a clock source forming a time base, delivering pulses III of high repetition rate r. The clock pulse source should be highly stable and capable of splitting up thescanning time of a line on the screen into equal time intervals of predetermined duration, 1. Each of the abscissas Xj of the character blocks are thus defined by a given number specifying the number of time intervals of duration 1' counted from the origin point of a line scan.

The pulses ly and Ix simultaneously control addressing circuits of the read and write circuits of memory 3, in such a manner that when a pair of pulses ly and Ix, indicating that scanning on the screen of a specific location of a character block may occur, the code of the character to be inscribed, or displayed, at that specific location will be present in the decoding unit 7. In order to insure necessary shift between decoding of a character code and display of the character, reading of the memory preferably follows the known principle of data-first, address-following reading. In other words, in a cycle of reading-writing of the memory 3, triggered by the appearance of the pulse pair Iy, Ix and indicating the beginning of a scan of a character block of coordinates Yi, Xj reading of the memory at an address corresponding to the location of the character block to be scanned will occur after the character block of coordinates Yi, Xj, for example at the location of the subsequent character block, having coordinates Yi, Xj+1, and then followed by writing of the address corresponding to the coordinates Xj, Yi. In this manner, as soon as the scanning of a character block of coordinates Yi, Xj+l starts, the reading of the character code to be inscribed in the block is terminated so that the code will be present in decoding unit 7.

The necessary synchronization signals to provide for time distribution occur on line 6 and include pulses Ix of period T, corresponding to the duration of the scanning of a portion of the line on the screen, the portion lying between the two abscissa division Xj and Xj+1 of two consecutive character blocks. The clock pulses, of recurrence frequency 1- and corresponding to q elementary segments from X1 to Xq of a portion of the preceding line are likewise derived from the clock source. The signals necessary for line distribution and occurring on conductor 5 group the line synchronization signals S, and the frame synchronization signals 8, of the television scanning raster such that the signals Iy will correspond to the start of the line scan of the successive message lines to be displayed. The use of these signals will be described below in connection with the electronic circuits which address the symbol memory.

The display system in accordance with the present invention utilizes a character, or symbol memory, which forms part of the unit 4( FIG. 2). The detail of this memory is illustrated in FIG. 5. A predetermined number of electro-luminescent sources S, and arranged in a line, as schematically indicated by the broken line 8,. S S, direct light towards a matrix plane M having matrix fields M,. M M,,,. The arrangement is such that the product of the numbers of the sources S and of the matrices M is equal to the total number of separate symbols, or characters which are to be reproduced. These characters or symbols are located on a support plane P, in form of a mask, arranged in fields having 1 lines and m columns. The number of sources, as has been noted, is equal to l, and the number of matrices, in a horizontal arrangement is equal to m. Each one of these sources are point sources, optically associated with a line, for example with line j of the mask P, and thus to the line of matrices M, to M,,,, such that the difierent symbols (or an optical inversion thereof, if desired) of a line j are successively illuminated, in proper order, on the difierent matrices. Thus, selection of a source S, for example source 5,, and of one matrix M,,-, for example, will provide read-out signals only from one mask element carried on mask plane P. In FIG. 5, character F is illustrated, at the intersection of line j and column k. The selection is controlled from information obtained from reading the code in the memory 3. Matrix M,- is, for example, formed of a group of photo-transistors, for example silicon transistors, located in a grid, or raster network having 2n lines and q columns, that is which will contain Znq individual elements located side by side, the number determining the definition which is required for the display of the symbols on the CRT screen. The mosaic of photo-transistors may be replaced, for example, by mosaics of any kind of photo-responsive devices, for example silicon photo-diodes, photo-transistors, or other elements.

When illumination is received from the sources S, the predetermined ones of the photo-electric devices on the matrix M are sensitized in accordance with the shape of the character on mask P. The duration of illumination is equal to the time T of the scanning of one character block separating two pulses Ix. Let it be assumed, for example that numbers 1 and m are each equal to 8, then the address code signals can identify one of 63 possible characters, resolved into two words of three bits each. One of the words will select one of the eight sources, and the other will select one of the eight matrices. These signals are derived from reading of the message memory 3, and may be grouped into three connecting lines, connected respectively to a decoder 71 for the source address, and a matrix decoder 72. FIG. 6 illustrates the electronic circuits associated with the matrix decoder. Each of the decoders has eight outputs. Connection to the sources is over power amplifiers l01....10j....10l. Optical devices, not shown, may be used to concentrate the emitted light energy from a source on a symbol line of the mask P. A practical and preferred solution utilizes electroluminescent diodes, having short on-off times and forming essentially a point source, supporting on its own structure optical arrangements. A suitable source is an electro-luminescent gallium arsenide diode, having optical lens elements applied to the light-emitting face and providing a cone-shaped light beam.

The addressing circuits for the matrices M1 to Mn may be as illustrated in FIG. 6 where the time distribution, as well as the selection circuits are illustrated.

The network which distributes the pulses to the various lines 11 is not shown in detail, since it may be a well-known logic circuit. It may be built, for example, by means of a counter, a delay line, or a shift register having 2n stages. Regardless how built, 2n lines of matrices are successively addressed, the addressing of a line of equal rank being simultaneous for all matrices, by serially connecting the outputs of the lines associated with the same rank. The construction may be such that interlace scanning of the fields can automatically be obtained.

In detail (referring to FIG. 6) the m outputs of decoder 72 are connected, respectively, to one of the switching circuits 121, 122....l2k, 12m, so that the matrixcan be selected. As-

sume, for example, that the identification code of a matrix during a time period T of scanning of one character block relates to matrix Mk. A signal will appear on the output connection of decoder which is connected to block 12k, and is simultaneously applied to q AND gates 131, 132, 13p, 13q, respectively connected to q columns of matrix Mk. Assume that the line of rank r is addressed by the distribution circuit for line 11, during the time T under consideration, then each photosensitive element carried on that line of matrix Mk and sensitized by the luminous beam such as, for example, element 15 of column p, will produce an electrical output signal applied to the second input of the AND circuit corresponding here to 13p. As a result, an output signal will be obtained from the AND circuit 13p.

A series ofq OR circuits 161, 162....16k, 16q, is grouped to provide a unique output from q connections. Thus n outputs from the matrices each having q connections will be provided from the selection switching system illustrated in FIG. 6. Each of the OR circuits has m inputs associated with m switching outputs of the same rank of a column such as OR circuit 16k, corresponding to m columns of rank p of the m matrices. All OR circuits are indicated as one group 16.

Power amplifiers 141, 14p, l4q, are provided in each one of the circuits 121, 122....12k, 12m, of the matrices M. These power amplifiers may be connected in any desired way; if the selection and switching networks operate at low level, for example, are of the integrated circuit type, the signals may be applied directly to the amplifiers at the output of the OR gates 16, to obtain a relatively high level signal for application to the q inputs to a logic circuit 17. In this case, the number of power amplifiers can be reduced by a factor of m over that illustrated in FIG. 6.

The time distribution is controlled by circuit 17 which receives, on the one hand, the q outputs from the OR gates 16, and on the other hand, synchronization signals Ix of clock l-I having the respective recurrence periods T and 1. Circuit 17 preferably consists of a shift register having q bistable circuits. During the scanning of one character block, the data corresponding to one line of the matrix, are thus transferred, in parallel, and load the register. The clock signal I-I triggers serial reading of the different data elements, in the desired order, at the successive instance of time, and the signal Ix then re-sets the register for reading of a subsequent character block in the same manner. The pulses received from the output of the register control the light of the read-out tube. In order to form black-level, or cancellation pulses, an inverter circuit 18, with an AND circuit 19 in series, may be provided (FIG. 6). The sampling of these complementary signals obtained from circuit 18 is done by triggering the AND circuit 19 at a frequency corresponding to the pulse repetition rate R, in the present example equal to the frequency of the clock signal. Other frequencies are also possible. Thus, blanking pulses are provided at those times when no brightness pulses are present. The pulses are applied to a bistable flip-flop circuit 20, switching over when the illumination pulses cause it to be triggered. The output of flip-flop 20 controls an amplifier 21 which delivers the display video signal V to a video output tube, well-known in the art and not shown. The signal delivered by the output flip-flop 20 provides a constant amplitude output, so that the successive pulses applied to the control circuit of the read-out tube will be of constant intensity, that is to say in the binary system, either providing maximum brightness or blanking.

These signals are delivered by circuit 8 during the course of the scanning of the line L1.

It is seen immediately that pulses D6, if taken sufficiently close together, can provide excellent precision of the definition of the segments to be displayed and consequently of the representation of the characters, without extending the spectrum of the video signals since the frequency of the pulses within the signals usually have a duration several times higher than the pulse duration of the period D6.

FIG. 7 illustrates, by way of example, a succession of light pulses A, and blanking pulses E, which appear at the output of flip-flop 20 during two time period T1 and T2 which follow each other; they are equal to the scanning period of a character block. The control pulses applied to the bistable flip-flop 20 then result in video output signals indicated at line V. Video signal V causes on scanning line L the appearance of a luminous trace, as illustrated schematically in FIG. 7. The display of entire characters is then obtained by successive traces, underneath each other. FIG. 7 illustrates a display of part of the characters C and B". As can be seen, the display is formed by segmental lines, built up of successive scanning lines, controlled by signals similar to the V signal (FIG. 7). The position and the length of each elementary segment of the scanning line is determined by coincidence with synchronization pulses. The display thus does not introduce non-linearities in case of vertical lines. Nevertheless, the position and the length of the elementary scanning lines is defined by whole multiples of elementary distances determined by the individual pulses; representation of contours of curves, or slanted line is, however, only approximate since the shift in position from one scanning line to the next can be only in coincidence with the individual pulses. Nevertheless, excellent definition and faithful following of curves can be obtained, much better than indicated on the schematic, highly enlarged representation on FIG. 7; by choosing the recurrence rate of the pulses sufficiently high, the accuracy with which curved portions can be reproduced is further increased.

The solution in accordance with the present invention is particularly advantageous with respect to other time distribution systems, and particularly with respect to other real time systems, due to the use of matrices. High resolution can be obtained with minimum complexity of equipment, and with low access time, determined only by the operating time from the photo-sensitive elements of the matrices. In the example illustrated, only the logic circuit 17 includes components which must respond to high frequencies.

The optical system of FIG. 5 is arranged to project any one of the 1 lines of the symbols carried by mask P on the line of the photo-transistor matrices M1 to Mm, each time respecting the rank of the m symbols of the line to be projected. For a particular given relative location of the mask and the phototransistors, a certain enlargement, by optical means, can readily be obtained. Optical symmetry can be achieved by various solutions. One utilizes a system in which the mask P is applied to a cylinder having an axis which corresponds to the median line of the matrices, each of the symbols having therewith associated an optical element, the optical elements between themselves being identical. The assembly of these optical elements is carried by a support which may be applied on a second cylinder, having an axis congruent with the axis of the mask cylinder. Referring to FIG. 8, a column of symbols is carried by mask P. When a symbol at the intersection of line j, and of column k is associated with optical element Ljk, an image will be formed on matric plane Mk. The cylindrical support L having axis X then carries 1.m identical objectives, located along 1 lines and m columns similar to a compound lenticular optic, formed of individual lenslets, like a flys eye. Projection of the various symbols is on a focal plane which is perpendicular to the optical axis of the particular lenslet. This plane is, however, more inclined with respect to the plane of the matrices as the line corresponding to the symbol is removed from the central line. In order to overcome this disadvantage, and further to eliminate parasitical interferences of illumination of one symbol next to the one selected, the actual surface occupied by the symbol within a symbol block is reduced, to leave a marginal separation zone with respect to adjacent symbols. The surface actually occupied by the symbol representation is illustrated in FIG. 8 by cross-hatching, the dimensions of which and the location are selected in accordance with the rank of the line under consideration in order to best compensate for optical projection conditions of the image representation on the entire surface of the associated matrices. t

The system of FIG. is not the only projection arrangement which can be used for the present invention; the number of sources may be increased by a predetermined factor, decreasing the number of matrices by an equal factor; for example, 16 sources located in two columns may be used with only four matrices for a total of 64 symbols. Technical characteristics of elements will determine the relative distribution of the sources and matrices; for example brightness and illumination power of photo-emissive diodes, sensitivity of photo-responsive units of the matrices, and relative prices of the elements will be determinative. The structure described in FIG. 5 requires a minimum number of 16 elements for 64 symbols. The electronic part may be simplified when one source is used for each symbol, requiring but a single matrix. The sources are then located on a grid, or raster, of 1 lines and m columns. The system in accordance with FIG. 8, utilizing one electro-luminescent source for each symbol, will then be modified such that the mask P and the compound lenticular optics (flys eye optics) L will be applied on concentric spheres, having a center 0, which also forms the center of a single matrix. The electronic circuits required will then only be a decoder for the selection of a source; the outputs from the columns of a single matrix can then be connected directly to a shift register 17 where the time distribution is effected.

The optical-electronic arrangement preferably includes complementary optics. Thus, in case of a single matrix, the optical system may be as indicated schematically in FIG. 9, which represents a plane developed view. A fiys eye optic, that is a compound lenticular optic L, is located on a plane surface, parallel to the plane of the symbol carrier or mask P. The sources S each are associated with a respective lenslet of another compound lenticular optic assembly, for example having u lenslets, each respectively associated with the emissive face of a diode; thus, a lenslet will be associated with diode Sjk, producing parallel rays. Each lenslet Ljk of assembly L projects the representation of the associated symbol by parallel rays. The optical distribution L is followed by a single optical element R, covering all of the lenslets of the compound lenticular optic (flys eye optic) and projects any one of the symbols illuminated on matrix plane M. Thus, selection of the source Sjk selects a particular symbol representation on mask P and projects this representation on the single matrix M.

The optical distribution of this arrangement, or of different arrangements, may readily be adapted to the system described in FIG. 5, for example providing a plane mask structure carrying the symbols, subdivided in any desired way regarding the sources and matrices.

The preceding discussion has assumed that the character blocks, for the symbols to be displayed, all had the same format and size, both regarding width and length. The format of any character block may readily be changed from one to the other, even on a single message line. In order to modify the height of a character inscribed in the character block, a shift means may be added to the line distribution system, to modify the distribution during the scanning of the character blocks under consideration. In order to decrease the height of the characters, for example by half, the signal transmission can be so controlled that only every other line, from a character as scanned, is actually displayed. In order to increase the height of the characters, various successive signals, vertically displaced, may be commanded for each scanning of the character; thus, each elementary character line may be displayed several times. Control of variation of the height of the characters can be programmed as a function of the character blocks being scanned, for each line of the screen, such that specific character blocks are increased or decreased in height, or that specific entire lines are increased or decreased.

In order to change the size of a character, one may also vary the time distribution, so as to suppress, or repeat the display of certain columns, for example, every other column of a character block. Other solutions may be, for example, to modify the frequency of the pulse repetition rate of the time D6 defining the length of the segments which constitute a specific character, to be displayed. If the time distribution is obtained by a delay line, various delay lines of different delay times may be used, to be switched in accordance with desired change in size. If the timing circuit is a shift register, the frequency of advance of the register may be used to change size of the character blocks; simultaneously, the recurrence time 1- of pulses H may likewise be changed; variations in size may thus be separately obtained for one, or more specific character blocks, within a line or for the entire line.

The size of the character blocks themselves may vary with the particular character to be inscrilbed; for example, a character block recording a I can be smaller than that recordinga W. This can be obtained by providing a zero reset circuit in the time distribution network, in order to stop scanning after a certain predetermined period of time, corresponding to the size of the character, for example a narrow character has elapsed, and permitting, however, normal scanning for subsequent, or large characters. The reduction in width of the character blocks may be controlled by the decoding circuit each time when a reduced-size character is read into the memory; alternatively, the reduction may be controlled each time a character block is read.

The geometrical dimensions of the symbols to be displayed may be changed by varying the geometrical position of the ele ments.

The system in accordance with the present invention has a number of advantages with respect to the display systems of the prior art. One of the primary advantages is the electronic simplicity, the electro-optical memory storing data in an arrangement which can readily be changed by simply changing the mask. The mask itself may be of small dimension, such as a few square centimeters, for example fitting on a standard frame of a 36mm. film, that is 24 X 36mm. The entire data storage thus can be installed in a very small volume, for example less than liter, and can be operated with low power consumption, for example merely a few hundred milliwatts. The arrangement in accordance with FIG. 6 may readily be built up of integrated circuits, and all logic circuits can be assembled on a single support or card.

The term symbol as used in the present invention is intended to convey the meaning of a predetermined shape to be displayed on a screen, and located within a character block. These symbols may be alphanumeric, but may also form any kind of curve, or curve element desired, and may further be an assembly of defined points within the space of a character block. Elementary curve forms thus are easily included within the term symbol; by proper assembly of such elementary curve forms, designs extended over several character blocks may be displayed on the screen, each one of the character blocks itself containing an elementary curve. If the mask itself is provided with a number of predetermined forms and shapes of elementary curves, each within a character block, a great variety of different curves may be displayed on a television screen, depending on the different combinations. The system of the present invention additionally may be utilized for displaying symbols, such as alphanumeric characters, super-imposed on a television image. This application is particularly useful in connection with programmed television teaching aids.

The present invention has been described in connection with line-byline scanning. Other types of scanning, such as spiral or circular, may be used; and various modifications and changes within the scope of the invention concept may be made.

We claim:

1. Symbol display system to convert messages of symbols presented thereto in coded form to obtain a display read-out of said messages having a cathode ray tube screen scanned line by line in a television-type raster, the display being read out on said cathode ray tube screen,

each symbol occupying a symbol block of predetermined horizontal width and extending, vertically, along a predetermined number of scanning lines,

each symbol being defined by a plurality of luminous elementary points subdivided into a field formed of said lines and of columns in said symbol-block,

the system comprising:

scanning means providing horizontal and vertical scanning signals (SL, ST) to said display screen; message memory means (2-3-7) receiving a. said scanning signals and b. coded signals representative of the identification of the different symbols to be displayed successively and of their respective location in said successively scanned symbol-blocks, said message memory means storing signals representative of the addresses of the different symbols to be displayed; symbol memory means (4-8) connected to and receiving from said message memory means c. time selection signals (5-6) corresponding successively to the symbol location of the symbols to be displayed in the successive scanned symbol-blocks, and d. address signals of said successive symbols, said symbol memory means storing representations representative of the different symbols contemplated; said symbol memory means comprising (FIGS. 5 and 6) at least one electroluminescent source (S), masking means (P) carrying representations of 14 symbols in the form of variable transparency on a support, each symbol occupying an elementary rectangular area in a grid network having 1 lines and m columns defining u of said elementary areas, each carrying a different symbol; at least one matrix (M) each having a photosensitive surface formed by a mosaic field of photo-sensitive detectors; and

symbol selection means controlled by said time selection signals and including logic means providing the selection of the elementary area carrying the symbol to be displayed at the instant considered, by selecting at least one electro-luminescent source and at least one matrix, the light emitted by one of said selected sources being directed through said selected area on one of said selected matrices, the number of electro-luminescent sources and the number of matrices being related to provide a product equal to the number it of different symbol contemplated;

said photo-sensitive detectors of said selected matrix being scanned electrically by said logic means to provide the video display signal on the part of the horizontal display scanned line and located in the symbol-block having the coordinates corresponding to the location of the selected symbol of the message to be displayed.

2. System according to claim 1 wherein each said electro-luminescent source comprises a plurality of point sources having short time turn-on, turn-off characteristics.

3. System according to claim 2 wherein said electroluminescent sources are gallium-arsenide diodes having optical light transmission means at their light output faces.

4. System according to claim 1 wherein each said matrix comprises a grid network of photo-transistors, the number of such photo-transistors in each line and column being determined by the required definition of the display of said display surface.

5. System according to claim 4 wherein said display surface is a cathode ray tube screen having the output of said phototransistors applied as intensity control signals.

6. System according to claim 1 wherein a plurality (1) of electro-luminescent sources is provided, arranged in line and matching a line of the raster of said masking means,

said electro-luminescent sources being electrically energized to provide illumination for a line of the raster of said masking means; and optical means are provided directing the beam from a selected source to a selected column of said raster, whereby a specific symbol will be selected. 7. System according to claim 1 including compound lenticular optics formed of a plurality of optical elements on a common support, said lenticular optics being located in lighttransmitting relation between said sources and said masking means.

8. System according to claim 7 wherein said masking means (P) is flat and an optical objective lens is associated with said compound lenticular optics.

9. System according to claim 7 including an additional compound lenticular optics (L), having u optical objective lenslets of predetermined enlargement power, optically associated with u symbols on said masking means (P), said additional lenticular optics being located between said masking means and said matrix and being of cylindrical shape said masking means also being cylindrical and having an axis congruent with the axis of said additional lenticular optics.

10. System according to claim 1 wherein the area occupied by said different symbols within said elementary blocks is less than thearea of said blocks to leave a marginal area, the relative dimensions of said symbols and said marginal areas being selected to provide for projection of said symbols on the individual photo-sensitive detectors of the matrix independently of the position of the symbol on said masking means.

11. System according to claim 1 in which a plurality of matrices are provided, logic circuits associated with said matrices and amplifier circuits connected to the outputs of said matrices, and selection circuits are provided transferring during each scanning period of a line of an elementary block the data derived from the selected matrix during said period and applying said data to a time distribution circuit.

12. System according to claim 11 wherein said time distribution circuit is a shift register.

13. System according to claim 11, wherein said selection circuits are low-level logic integrated circuits.

14. System according to claim 1, including a single matrix, and wherein u electroluminescent sources are provided, and logic circuits are associated with the columns of the matrix and including amplifying and time distribution circuits; and addressing circuits connected to said electro-luminescent sources.

15. System according to claim 14 wherein compound lenticular optics formed of a plurality of lenslets are provided, said mask (P) and said compound lenticular optics being spherical, and concentric with respect to each other and located at a central point with respect to the surface of said matrix.

16. System according to claim 14 including compound lenticular optics formed of a plurality of lenslets, said electroluminescent sources being located in a plane, optically associated with said compound lenticular optics;

said mask being plane; and

a second compound lenticular optics similar to said first compound lenticular optics associated with said mask; and

objective means focusing light on said matrix. 

1. Symbol display system to convert messages of symbols presented thereto in coded form to obtain a display read-out of said messages having a cathode ray tube screen scanned line by line in a televisiontype raster, the display being read out on said cathode ray tube screen, each symbol occupying a symbol block of predetermined horizontal width and extending, vertically, along a predetermined number of scanning lines, each symbol being defined by a plurality of luminous elementary points subdivided into a field formed of said lines and of columns in said symbol-block, the system comprising: scanning means providing horizontal and vertical scanning signals (SL, ST) to said display screen; message memory means (2-3-7) receiving a. said scanning signals and b. coded signals representative of the identification of the different symbols to be displayed successively and of their respective location in said successively scanned symbolblocks, said message memory means storing signals representative of the addresses of the different symbols to be displayed; symbol memory means (4-8) connected to and receiving from said message memory means c. time selection signals (5-6) corresponding successively to the symbol location of the symbols to be displayed in the successive scanned symbol-blocks, and d. address signals of said successive symbols, said symbol memory means storing representations representative of the different symbols contemplated; said symbol memory means comprising (FIGS. 5 and 6) at least one electroluminescent source (S), masking means (P) carrying representations of u symbols in the form of variable transparency on a support, each symbol occupying an elementary rectangular area in a grid network having 1 lines and m columns defining u of said elementary areas, each carrying a different symbol; at least one matrix (M) each having a photosensitive surface formed by a mosaic field of photo-sensitive detectors; and symbol selection means controlled by said time selection signals and including logic means providing the selection of the elementary area carrying the symbol to be displayed at the instant considered, by selecting at least one electroluminescent source and at least one matrix, the light emitted by one of said selected sources being directed through said selected area on one of said selected matrices, the number of electro-luminescent sources and the number of matrices being related to provide a product equal to the number u of different symbol contemplated; said photo-sensitive detectors of said selected matrix being scanned electrically by said logic means to provide the video display signal on the part of the horizontal display scanned line and located in the symbol-block having the coordinates corresponding to the location of the selected symbol of the message to be displayed.
 2. System according to claim 1 wherein each said electro-luminescent source comprises a plurality of point sources having short time turn-on, turn-off characteristics.
 3. System according to claim 2 wherein said electroluminescent sources are gallium-arsenide diodes having optical light transmission means at their light output faces.
 4. System according to claim 1 wherein each said matrix comprises a grid network of photo-transistors, the number of such photo-transistors in each line and column being determined by the required definition of the display of said display surface.
 5. System according to claim 4 wherein said display surface is a cathode ray tube screen having the output of said photo-transistors applied as intensity control signals.
 6. System according to claim 1 wherein a plurality (1) of electro-luminescent sources is provided, arranged in line and matching a line of the raster of said masking means, said electro-luminescent sources being electrically energized to provide illumination for a line of the raster of said masking means; and optical means are provided directing the beam from a selected source to a selected column of said raster, whereby a specific symbol will be selected.
 7. System according to claim 1 including compound lenticular optics formed of a plurality of optical elements on a common support, said lenticular optics being located in light-transmitting relation between said sources and said masking means.
 8. System according to claim 7 wherein said masking means (P) is flat and an optical objective lens is associated with said compound lenticular optics.
 9. System according to claim 7 including an additional compound lenticular optics (L), having u optical objective lenslets of predetermined enlargement power, optically associated with u symbols on said masking means (P), said additional lenticular optics being located between said masking means and said matrix and being of cylindrical shape said masking means also being cylindrical and having an axis congruent with the axis of said additional lenticular optics.
 10. System according to claim 1 wherein the area occupied by said different symbols within said elementary blocks is less than the area of said blocks to leave a marginal area, the relative dimensions of said symbols and said marginal areas being selected to provide for projection of said symbols on the individual photo-sensitive detectors of the matrix independently of the position of the symbol on said masking means.
 11. System according to claim 1 in which a plurality of matrices are provided, logic circuits associated with said matrices and amplifier circuits connected to the outputs of said matrices, and selection circuits are provided transferring during each scanning period of a line of an elementary block the data derived from the selected matrix during said period and applying said data to a time distribution circuit.
 12. System according to claim 11 wherein said time distribution circuit is a shift register.
 13. System according to claim 11, wherein said selection circuits are low-level logic integrated circuits.
 14. System according to claim 1, including a single matrix, and wherein u electroluminescent sources are provided, and logic circuits are associated with the columns of the matrix and including amplifying and time distribution circuits; and addressing circuits connected to said electro-luminescent sources.
 15. System according to claim 14 wherein compound lenticular optics formed of a plurality of lenslets are provided, said mask (P) and said compound lenticular optics being spherical, and concentric with respect to each other and located at a central point with respect to the surface of said matrix.
 16. System according to claim 14 including compound lenticular optics formed of a plurality of lenslets, said electroluminescent sources being located in a plane, optically associated with said compound lenticular optics; said mask being plane; and a second compound lenticular optics similar to said first compound lenticular optics associated with said mask; and objective means focusing light on said matrix. 